The present invention relates to a cap for use with a cannula and, more particularly, to a cap having a valve for resealably providing access to the interior of a cannula.
A prior art cannula is shown in FIG. 1 and includes a flexible body 10 having a flexible end 12 for insertion into a blood vessel. Prior to insertion of the cannula into the blood vessel, a needle 14 must be inserted through the cannula such that the pointed end of the needle extends beyond the flexible end 12. The needle allows the cannula to be guided through a patient's skin and to penetrate the blood vessel as the cannula 10 is inserted therein.
Subsequent to the insertion of the flexible end 12 into a blood vessel, the needle 14 is extracted in order to allow the insertion of a tube for allowing passage of blood or other fluids to r from the cannula 10 through the tube. In order to provide a proper seal around the needle and the tube inserted into the cannula and to prevent blood from flowing out of the cannula when the needle is extracted, a cap member 16 is provided positioned on the end of the cannula 10 and includes a plurality of slits extending radially across the center of the cap 16 for providing a recloseable opening for insertion of the needle and tube therethrough.
A recurring problem with the above-described arrangement is the prevention of small leaks through the slits in the cap member after the needle 14 has been withdrawn.
One prior art solution for properly sealing a cannula is shown in U.S. Pat. No. 4,655,752 issued to Honkanen et al in which a pair of seal members are provided for closing off the end of a cannula. In particular, a first seal member is provided having a conical shape and a cruciform slit for permitting passage of a surgical instrument therethrough. It is disclosed that fluid pressure will force the cruciform slit portion to contract together to form an impervious seal to fluid flow. However, such a construction depends on the seal members defining the slit being in proper alignment with each other in order to prevent fluid flow and therefore requires that the end portions of the seal be formed as a sufficiently stiff structure to prevent collapse of the seal members in toward each other. In order to prevent fluid flow past the first seal member when a tube is inserted therethrough, a second seal member lacking slits is required to sealingly contact the tube. Thus, two seals are required to effectively prevent flow through the valve portion of the cannula.
Accordingly, there is a need for a cap member having a valve portion which will reliably reseal the cannula end after removal of an instrument or tube therefrom. In addition, there is a need for a cap member which will provide an effective seal around the exterior of an instrument or tube which has been inserted into fluid communication with the interior of a cannula.